1. Field of the Invention
This invention relates to methods and means for culturing or detecting microorganisms in contact with a nutrient-incorporated web matrix.
In the diagnosis of microbial derived diseased conditions in man and animals, it is often highly useful to determine the particular causative microorganisms. This is particularly true in the diagnosis of the venereal disease gonorrhea which is the direct result of infection with the microorganism Neisseria gonorrhoeae. Many methods have evolved from the search for specific microbial identification tests, including the use of colorimetric indicators and immunochemical indicators. Nonetheless, the conventional diagnosis of certain microbial derived diseases remains based on microbiological culture techniques.
2. Description of the Prior Art
Conventional microbiological techniques used in diagnosis of microbial derived diseases involve an in vitro culturing of a test sample obtained from the subject under diagnosis. The culturing media used may be either capable of supporting the growth of a broad spectrum of microorganisms or selective to a small number of microorganisms or even a single strain of microorganism. Generally the object of using an all-purpose medium is to isolate pure colonies from the sample and thereafter to analyze them either chemically or biologically in order to identify pathological microorganisms in the sample. When a selective media is used, one knows if a certain group or variety of microorganisms is present or absent in the sample based on a growth or no-growth observation. It is therefore critical to such microbiological techniques to have available appropriate culturing techniques for those microorganisms of pathological significance.
The contemporary clinical laboratory is in great need of more rapid and convenient culturing methods and means. At the present time, clinical microbiological techniques are based almost exclusively on the use of poured agar plates. It is well known that such agar plates have a very short shelf life and are extremely cumbersome to use. Some synthetic gels have been developed as proposed substitutes for the agar base in the poured plates but they have not been proven to be any more stable or easy to use. Just recently, culturing devices comprising a nutrient-incorporated web matrix or absorbent pad have been developed which have proven to be useful substitutes for the disadvantageous agar plates. Such devices provide a substantially dry web matrix incorporated with microbiological nutrients which can be stored for many months and then rehydrated for use in the culturing of microorganisms. Such a device is described in U.S. Pat. No. 3,881,993 assigned to the assignee hereof.
These devices have been found to be adaptable for the cultivation of a wide variety of microorganisms, including fairly fastidious microorganisms, i.e., those requiring very carefully controlled nutrient media and/or atmospheres. For instance, a highly useful culturing means has been designed based on the use of a nutrient-incorporated web matrix for the growth and detection of the delicate microorganism Neisseria gonorrhoeae as disclosed in U.S. Pat. No. 3,888,741, also assigned to the assignee hereof.
The matrix culturing devices of the prior art have not been entirely satisfactory, however, for use in the culturing of osmotically sensitive microorganisms. In the web matrix type devices, the growing microorganisms are more or less surrounded by a liquid environment and may be found dispersed throughout the interior portion of the web matrix, in contrast to conventional agar plates where the growing microorganisms are supported on the gel surface. Because of this critical distinction, it has been found that in order to prepare a useful web matrix type culturing device to correspond to a particular conventional agar plate, it is oftentimes not merely a simple matter of incorporating the nutrient ingredients from the agar medium formulation into a web matrix structure. One instance where this has been found to be the case is in the culturing of osmotically fragile microorganisms, particularly N. gonorrhoeae.